1. Field of the Invention
The present invention relates to hoists and in to particular to water craft hoists of the type generally affixed to the aft end of boats.
2. Description of the Related Art
It has become increasingly common for large private water craft, or yachts, to transport auxiliary water craft such as dinghies, jet skies, PWCs and the like. While it has been generally known to mount such auxiliary craft to an upper deck or roof structure and to utilize cranes for loading and unloading, many boat designs are ill adapted for such use. Recently it has become more common to provide a replacement swim platform or platform extension at the aft end of the vessel and to equipment the platform with chocks to cradle the auxiliary craft. Loading and unloading heavy auxiliary craft to and from an out of water platform still requires the use of a crane or other hoist.
More recently, powered platforms, or boat lifts, capable of raising and lowering with respect to the host boat have been proposed. Such devices have included telescoping vertical structures carrying horizontal supports or arms to which a platform or boat chock set can be affixed. It has been known to power the telescoping structures both by individual hydraulic cylinders, such as shown in U.S. Pat. No. 5,544,606 or by means of motor driven cables such as shown, for example, in U.S. Pat. No. 4,878,450.
While such devices may work satisfactorily for consistently weighted auxiliary craft, they may experience difficulties with properly lifting, lowering and supporting water craft which are heavier at one end than the other. Since it is common to utilize aft of center engine and propulsion placement in auxiliary craft, generally the aft section is heavier than the bow section. Such unequal weighting provides unequal loading on horizontally spaced vertically moveable supports.
It would be an advance in the art to provide a self-leveling device where unequal weight distribution of the auxiliary craft would not cause tilting, cocking or binding of the lifting system. It would be a further advance in the art to utilize hydraulic power while eliminating the need for multiple hydraulic cylinders in an auxiliary water craft lifting device.
It would be a further advance in the art to utilize a single double acting hydraulic cylinder which is enclosed and maintained out of the water and which drives a cable system for raising and lowering an auxiliary water craft support structure.
This invention provides a hydraulically powered, cable connected, vertically extensible and retractable auxiliary water craft lift which is attachable to the aft end of a host vehicle and which raises and lowers an auxiliary water craft support structure with respect to the host boat so that the support structure may be lowered into the water allowing the auxiliary water craft to float free of its support and can thereafter be raised above the water to lift the auxiliary water craft above the water surface.
In a preferred embodiment of my invention, I provide a first U-shaped base structure which is to be stationary mounted to the hoist boat, preferably at the aft end, and usually to the stern transom. This U-shape structure is substantially out of the water and includes an upper horizontal member which contains a double acting hydraulic cylinder and a horizontally moveable truck. Vertically positioned legs at either end of the horizontal member include cable directing sheaves for routing lifting and lowering cables attached to the horizontally moveable truck. The vertical legs also receive movable connectors which in turn are connected to vertically movable intermediate members which, based upon the direction of movement of the truck are raised or lowered with respect to the vertical legs by the cables. The intermediate moveable members in turn extendably and retractably carry support posts. Cables connected to the support posts and to the vertical legs are trained around sheaves in the intermediate members causing the support posts to extend and retract vertically with respect to the intermediate members as a result of movement of the intermediate members with respect to the vertical legs.
The support posts in turn carry platform supporting arms to which either a platform or water craft support cradle is attached. By utilizing cables driven by the hydraulic cylinder movement of the support arms is coordinated irrespective of the weight distribution between the support arms.
It is therefore an object of this invention to provide an improved boat lift structure for mounting to hoist boats.
It is another, and more specific object of this invention to provide hydraulically driven, cable actuated, auxiliary water craft raising and lowering device utilizing a single hydraulic cylinder to operate spaced extending and retracting water craft support arms.
It is an object of this invention to provide an auxiliary water craft hoist system to be affixed to the aft of larger water craft, the system employing a U-shaped structure with a horizontal member carrying a single double acting hydraulic cylinder with depending vertical members providing a cable assembly affixed to the hydraulic cylinder and to vertically extendable and retractable members which are in turn operatively connected to an auxiliary water craft support structure.
It is an object of this invention to provide a cable driven, hydraulically powered, auxiliary water craft support hoist for attachment to host vessels employing a single double acting hydraulic cylinder which moves a truck member having a cable connected to it which in turn raises and lowers vertically disposed intermediate members which in turn utilize cabling to vertically move support posts carried by the intermediate members.
These and other objects of the present invention will be understood from the following description of the preferred embodiment by way of an example.